Pressure viscosity compensating flow control device

ABSTRACT

A flow control device responsive in operation to variations in pressure and viscosity of the fluid flowing therethrough utilizes a flexible diaphragm having a pressure drop orifice therein movably mounting a spool and valve element which is also biased by an adjustable tensioning means. Differential pressures on the opposite sides of the flexible diaphragm occasioned by the pressure drop orifice therein results in maintaining uniform pressure to flow ratio. An elongated restricted passageway in the spool senses changes in viscosity in the fluid flowing through the device by reason of a corresponding pressure drop along the same which results in moving the spool and valve element to hold the flow through the device as desired. The device is described in a hand paint spray gun wherein changes in pressure and viscosity of the paint flowing through the gun occur and the flow is held by the device as desired, thus, enabling the paint gun to maintain the desired pressure on the nozzle at all times regardless of changes in paint pressure or paint viscosity.

United States Patent [72] Inventors Frank Welty 4962 Lockwood Blvd.;Raymond D. Welty, 4307 Lake Road, Youngstown, Ohio 44511 [21] Appl. No.775,846 [22] Filed Nov. 14, 1968 [45] Patented Feb. 23, 1971 [54]PRESSURE VISCOSITY COMPENSATING FLOW CONTROL DEVICE 9 Claims, 3 DrawingFigs.

[52] U.S. (I 137/240, 137/495,137/501,l37/614.21 [51] Int. G05d 7/01[50] Field ofSearch .137/501, 495, 500, 614.21, 240

[56] References Cited UNITED STATES PATENTS 1,743,127 1/1930 Fuller137/495 2,637,339 5/1953 Pease 137/501 FOREIGN PATENTS 1,077,937 11/1952Germany 137/501 Primary Examiner-M. Cary Nelson Assistant Examiner-R. B.Rothman Att0rneyWebster B. I-Iarpman ABSTRACT: A flow control deviceresponsive in operation to variations in pressure and viscosity of thefluid flowing therethrough utilizes a flexible diaphragm having apressure drop orifice therein movably mounting a spool and valve elementwhich is also biased by an adjustable tensioning means. Differentialpressures on the opposite sides of the flexible diaphragm occasioned bythe pressure drop orifice therein results in maintaining uniformpressure to flow ratio. An elongated restricted passageway in the spoolsenses changes in viscosity in the fluid flowing through the device byreason of a corresponding pressure drop along the same which results inmoving the spool and valve element to hold the flow through the deviceas desired.

The device is described in a hand paint spray gun wherein changes inpressure and viscosity of the paint flowing through the gun occur andthe flow is held by the device as desired, thus, enabling the paint gunto maintain the desired pressure on the nozzle at all times regardlessof changes in paint pressure or paint viscosity.

sum 2 [1F 2 PATENTED FEB23 I971 INVENTORS FRANK WELTY a BYRAYMOND 0.WELTY ATTORNEY Q45 mu.

ix zrwwll. 'lIIII/WI PRESSURE VISCOSITY COMPENSATING FLOW CONTROL DEVICEBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to pressure and viscosity compensating flow control devices suchas used to maintain the desired flow of fluid regardless of changes inthe source pressure and viscosity of the fluids being handled.

2. Description of the Prior Art Prior structures of this type haveutilized pressure control means consisting of valve elements biased byspring means and acting to move the valve element relative to a valveorifice upon increases or decreases of the pressure in the fluid beingcontrolled. Such devices have had a common objection in being subject ofa hunting action in which the valve element constantly moves seeking anintermediate position and actually over travelling with the result thatan erratic pressure control results. Typical of such prior art are 11.8.Pats. Nos.

3,130,747; 2,255,787 and 2,984,261. No prior art is known with respectto the flexible diaphragm having the pressure drop orifice therethroughand directly supporting and moving a spool and valve element. Pats.3,351,087 and 3,335,749 are the only prior art structures knownutilizing differential pressures on the opposite sides of pistons andPat. No. 3,335,749 discloses an elongated viscosity restrictor.

This invention incorporates means for introducing a solvent into thedevice to quickly clean paint or similar material therefrom.

SUMMARY OF THE INVENTION A pressure viscosity compensating flow controldevice particularly suitable for use in a hand paint gun having aflexible diaphragm supporting a spool and valve element in a housing andarranged so that inlet source pressure of the paint is supplied to oneside of the diaphragm so as to urge the spool and valve element in onedirection and against a spring tensioning member to thereby tend toclose the valve element relative to a valve seat in the housing andwherein the diaphragm incorporates a pressure drop orifice establishingcommunication to the other side thereof to create a differentialpressure acting to oppose the adjustable spring tensioning unit intending to move the spool and valve element away from the valve seat inthe housing. The spool incorporating an elongated pressure droprestriction, so that it is responsive to changes in the viscosity offluid and varies the position of the valve element which is responsiveto such viscosity changes as well as pressure changes.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross sectional side elevationof a paint gun incorporating the pressure-viscosity compensating flowcontrol device.

FIG. 2 is a cross sectional side elevation of a modified paint gunwherein the spool of the device is interconnected with a movable memberin the tip of the paint gun so that the size of the spring orifice maybe altered along with the flow and responsive to changes in sourcepressure and viscosity in the material flowing through the gun.

FIG. 3 is a cross sectional side elevation of the pressureviscositycompensating flow control.

DESCRIPTION OF THE PREFERRED EMBODIMENT A pressure drop orifice 18establishes communication between the cavity 17 and the cavity in thehousing portion 11.

The diaphragm 14 receives and supports a valve spool 19 which ispositioned partially within the cavity 15 and partially within alongitudinal chamber 20 in the housing portion 10. The spool 19 ishollow throughout most of its length and defines a restricted passageway21 by reason of a fixed rod 22 extending axially thereof and mounted ona plug 23 in an opening in the portion 11 of the housing. A compressionspring 24 is positioned against the inner end of the plug 23 and againsta shoulder in the spool 19.

A valve seat 25 is formed in the housing portion 10 and a valve element26 on an extension of the spool 19 is registerable in the valve seat 26.The fluid passageway 21 extends through openings 27 in the spool 19 andcontinues around the extension supporting the valve element 26 and thenthrough the valve seat 25 and the outlet opening 13.

It will thus be seen that fluid introduced into the device through theinlet opening 12 enters diaphragm cavity 17 and tends to move thediaphragm toward the cavity 15. It then flows through the pressure droporifice 18 and into the cavity 15 where it creates a differentialpressure against the other side of the diaphragm 14. It then flowsthrough the passageway 21, the openings 27 and the elongated chamber 20through the valve seat 25 and is thereby controlled by the valve element26. If a pressure increase in the source of supply occurs, the pressuredrop across the pressure drop orifice 18 would also increase causing thespool 19 to move against the spring 24 and partially close the valveseat 25 by movement of the valve element 26 thereby holding the flow tothe outlet opening 13 constant. Conversely, a decrease in fluid pressureat the inlet orifice 12 would decrease the pressure drop across thepressure drop orifice 18 allowing the spring 24 to move the spool 19 tofurther open the valve element 26 with respect to the valve seat 25 tomaintain the pressure at the outlet orifice 13 constant.

Should an increase in viscosity in the fluid flowing through the deviceoccur do for example to a decrease in temperature or loss of solvent,the pressure drop across the long viscosity restrictor comprising theelongated passageway 21 would override the increased pressure dropacross the pressure drop orifice l8 and allow the spring 24 to move thespool 19 to further open the valve element 26 with respect to the valveseat 25 thereby holding the flow to the outlet orifice 13 constant.Conversely, should the viscosity of the fluid flowing through the devicedecrease the pressure drop across the restrictor comprising theelongated passageway 21 would decrease thereby allowing the diaphragm 14to move the spool 19 to partially close the valve seat 25 with the valveelement 26 thereby continuing to hold the flow to the nozzle constant.

By referring now to FIG. 1 of the drawings, it will be seen that thepressure-viscosity compensating flow control just described in FIG. 3has been incorporated in a hand paint gun wherein the inlet orifice 27communicates by way of a check valve 28 with a diaphragm cavity 29 in atwo-part diaphragm 30 and 31 respectively, the parts being spaced tocreate the diaphragm cavity 29 and positioned in a paint gun housing 32which also defines a secondary cavity 33. The paint gun housing 32 hasan extension 34 with an elongated chamber 35 therein in which a spool 36is positioned and supported by the diaphragm 30 in the same manner asthe spool 19 is supported by the diaphragm 14 isthe embodiment of thethe invention i1- lustrated in FIG. 3 of the drawings and hereinbeforedescribed. An adjustment plug 37 engages a tension spring 38 which inturn engages a shoulder on the spool 36 and within a hollow interiorthereof which defines an elongated restrictor passageway 39 by reason ofan elongated plug 40 extending there into and which plug 40 is anextension of the plug 37. Openings 41 communicate with a restrictorpassageway 39 and the interior of the hollow extension 34 of the paintgun and convey liquid paint around the end of the spool 19 and anextension 42 thereon which carries a valve element 43 registerable witha valve seat 44 in the extension 34. A secondary valve 45 located inspaced relation to the valve element 43 and within the hollow extension34 of the paint gun is movable to provide on and off control of the gunand particularly with respect to a paint spraying nozzle construction ina tip 46 of the paint gun. The nozzle includes a paint passageway 47 anozzle orifice disc 48 and a control valve disc seat 49 with which thesecondary valve element 45 registers. The nozzle assembly is held by afitting 50 threadably engaged on the hollow extension 34 of the paintgun. The extension 34 of the paint gun has a secondary inlet port 51which communicates with the outermost surface of the portion 31 of thediaphragm 30 and which portion is provided with at least one one-wayintegral valved opening 52 formed of the material of the diaphragm 30and 31 and therefore resilient.

When a solvent source is placed in communication with the secondaryinlet opening 51 and the paint supply source normally communicating withthe inlet orifice 27 is disconnected the solvent will enter through thesecondary inlet orifice 51 and flow against the outer surface of thediaphragm part 31 through the one way valve opening or openings 52therein and into the diaphragm cavity 29 and then through the pressuredrop orifice 52 and into the secondary cavity 33 from whence it willflow through the testrictor passageway 39, the openings 41 and throughthe hollow extension 34 and its paint carrying passageways to andincluding the spray nozzle tip 46. Thus, solvent may be introduced toquickly clean out the paint gun and permit another color of paint to bepromptly handled thereby.

The operation of the paint gun with respect to the constant control offlow at varying pressures and viscosity by the compensating flow controlbuilt therein is exactly the same as that heretofore described inconnection with the flow control device of FIG. 3 of the drawings andthose skilled in the art will observe that paint flowing through thepaint gun illustrated in FIG. 1 will be subjected to thepressure-viscosity compensating flow control so that a constant flow ismaintained at the actual spray nozzle orifice at all times at varyingsupply pressures and varying paint viscosities. thereby preventingexcessive over spray or under spring and assuring proper atomization ofthe paint at the nozzle.

Those skilled in the art will observe that while the embodimentillustrated and described as related to a hand paint gun, it is alsoapplicable to a fixed paint spray nozzle assembly and, for example, agroup of such fixed paint nozzles within a paint tunnel or the like.

Those skilled in the art will observe that the compensating motion ofthe spool 19 of the device seen in FIG. 3 and the spool 36 of the handpaint gun seen in FIG. 1 may also be employed for varying theappropriate movable portions of a paint spray nozzle so as to vary thesize of a spray orifice and by referring to FIG. 2 of the drawings, amodified hand paint spray gun may be seen incorporating such amodification.

In FIG. 2 the paint gun housing comprises the body member 53 and itsextension portion 54. The portion 53 of the housing includes an endclosure 55 with is plugged orifice in which a plug 56 is located and thediaphragm 57 is spaced inwardly with respect to the closure 55 and formsa diaphragm cavity 58. The diaphragm is a two part diaphragm with asecond portion indicated by the numeral 59 and there is a pressure droporifice 60 extending through the diaphragm so that paint introducedthrough an inlet 61 passing a check valve 62 is present at the upper orouter surface of the two part diaphragm 57 59. It will then flow throughthe pressure drop orifice 60 into the diaphragm cavity 58 and thencethrough the center opening of the diaphragm and into the hollow spool 63by way of a restrictor passage 64 therein which is defined by anextension 65 on the plug 56.

Transverse passageways 66 convey the paint to the hollow interior 67 ofthe portion of the housing 54 where it can flow towards the nozzleassembly, It is first controlled by a valve element 68 on the spool 63which is registerable with a valve seat 69 and a lever 70 is arranged sothat this valve the numetal 68 can be manually moved to on or offposition thereby.

When it is in on position, it will be observed that the valve 68 iscapable of floating responsive to the pressure and viscosity control ofthe device as it is part of the spool 63. The nozzle assembly of the gunincludes a paint discharging orifice 71 and a second valve element 72movable therein and attached by way of an extension 73 to the forwardend of the spool 63. Thus, motion of the spool 63 will be imparted tothe secord valve element 72 which will thereupon vary the opening in thenozzle of the gun. The paint gun functions the same as the paint gunheretofore described in connection with FIG. 1 in that paint isintroduced into the chamber between the two parts of the diaphragm 57and 59, it flows through the pressure drop orifice into the diaphragmcavity 58 thus a differential pressure is created thereon which isresponsive to the pressure in the paint supply line. The spool 63 beingattached to and movable by the diaphragm 57 is thus responsive topressure fluctuations and opens and closes the second valve element 72relative to the valve seat 71 to provide a uniform pressure and flowthrough the nozzle assembly. The paint passes through the hollowinterior 67 around the rod and thus moves through the restrictorpassageway 64 which senses changes in viscosity and imparts movementrelative thereto to the valve spool 64. The valve spool 64 in themodified structure of FIG. 2 of the drawings incorporates the biasingspring 74 and the function and operation of the pressure-viscositycompensating flow control device is the same in this environment as itis in the embodiment heretofore described in connection with FIG. 3 ofthe drawings.

In the modification of FIG. 2 the compensating motion of the valve spoolnot only acts in the manner hereinbefore described by permits themovement of the valve element 68 relative to the valve seat 69 in an onand off control as by control of the lever 70.

Although but a few embodiments of the present invention have beenillustrated and described, it will be apparent to those skilled in theart that various changes and further modifications may be made thereinwithout departing from the spirit of the invention.

We claim:

1. A pressure-viscosity compensating fluid flow control deviceconsisting of a housing having inlet and outlet openings and a diaphragmchamber therein, a spaced pair of diaphragms in said chamber, a spoolhaving thru-bore positioned in said chamber engaging central openings insaid diaphragms, said inlet opening communicating with the space betweensaid diaphragms, an orifice in one of said diaphragms to conduct fluidto the other side thereof to said thru-bore in said spool whereby fluidflowing through said orifice is conducted to the other end of saidspool, an element on said other end of said valve spool for registrywith a valve seat communicating with said outlet port and resilientlyyieldable means biasing said spool against the axial force exerted bysaid diaphragms by reason of the pressure drop through said orifice.

2. The device of claim 1 and wherein the thru-bore is an elongatedpressure drop passageway acting as a viscosity sensor.

3. The device of claim 1 and wherein the diaphragms are integral.

4. The device of claim 1 and wherein the valve element is positioneddownstream of the valve seat.

5. The device of claim 1 having a secondary inlet opening communicatingwith the space between said diaphragms through which a second fluid maybe directed for flushing said device.

6. A device of passing a predetermined quantity of fluid per unit oftime regardless of variations in the pressure of the fluid source andvariations in the viscosity of the fluid comprising: a housing havingspaced inlet and outlet openings and a combined valve member and adiaphragm in said housing for controlling the flow of fluid between saidinlet opening and said outlet opening, means to conduct fluid from thesource to the side of the diaphragm which is toward the valve member tocreate a force on said diaphragm and to the other side of saiddiaphragm, to create an opposing force thereon, an orifice in said meansconducting said fluid to the other side of said diaphragm, secondarymeans to conduct fluid from said other side of said diaphragm to saidoutlet opening by way of said valve member and yieldable means biasingsaid valve member and diaphragm against the axial force exerted by saiddiaphragm by reason of pressure drop through said orifice.

7. The device of claim 6 and wherein said means conducting said fluid tothe other side of the diaphragm comprises an orifree through saiddiaphragm, said orifice acting to create said pressure drop.

8. The device of claim 7 and wherein said secondary means to conductfluid from said other side of said diaphragm to said outlet openingcomprises an elongated thru-bore in said valve member terminating shortof the end thereof, and wherein said end of said valve member engagessaid outlet opening.

9. The device of claim 6 and wherein said diaphragm is double with aspace therebetween and said means conducting fluid from said sourcecommunicates with said space.

1. A pressure-viscosity compensating fluid flow control deviceconsisting of a housing having inlet and outlet openings and a diaphragmchamber therein, a spaced pair of diaphragms in said chamber, a spoolhaving thru-bore positioned in said chamber engaging central openings insaid diaphragms, said inlet opening communicating with the space betweensaid diaphragms, an orifice in one of said diaphragms to conduct fluidto the other side thereof to said thru-bore in said spool whereby fluidflowing through said orifice is conducted to the other end of saidspool, an element on said other end of said valve spool for registrywith a valve seat communicating with said outlet port and resilientlyyieldable means biasing said spool against the axial force exerted bysaid diaphragms by reason of the pressure drop through said orifice. 2.The device of claim 1 and wherein the thru-bore is an elongated pressuredrop passageway acting as a viscosity sensor.
 3. The device of claim 1and wherein the diaphragms are integral.
 4. The device of claim 1 andwherein the valve element is positioned downstream of the valve seat. 5.The device of claim 1 having a secondary inlet opening communicatingwith the space between said diaphragms through which a second fluid maybe directed for flushing said device.
 6. A device of passing apredetermined quantity of fluid per unit of time regardless ofvariations in the pressure of the fluid source and variations in theviscosity of the fluid comprising: a housing having spaced inlet andoutlet openings and a combined valve member and a diaphragm in saidhousing for controlling the flow of fluid between said inlet opening andsaid outlet opening, means to conduct fluid from the source to the sideof the diaphragm which is toward the valve member to create a force onsaid diaphragm and to the other side of said diaphragm, to create anopposing force thereon, an orifice in said means conducting said fluidto the other side of said diaphragm, secondary means to conduct fluidfrom said other side of said diaphragm to said outlet opening by way ofsaid valve member and yieldable means biasing said valve member anddiaphragm against the axial force exerted by said diaphragm by reason ofpressure drop through said orifice.
 7. The device of claim 6 and whereinsaid means conducting said fluid to the other side of the diaphragmcomprises an orifice through said diaphragm, said orifice acting tocreate said pressure drop.
 8. The device of claim 7 and wherein saidsecondary means to conduct fluid from said other side of said diaphragmto said outlet opening comprises an elongated thru-bore in said valvemember terminating short of the end thereof, and wherein said end ofsaid valve member engages said outlet opening.
 9. The device of claim 6and wherein said diaphragm is double with a space therebetween and saidmeans conducting fluid from said source communicates with said space.